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Uterine tear or rupture in the mare

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Uterine tear or rupture in the mare

The correct position of a foal prior to being born ©Rob Lofstedt

What causes a uterine tear or rupture?

A uterine tear or rupture most commonly happens during the birth and rarely pre-partum but has been reported in cases of seemingly normal parturition as well as in mares with uterine torsion or during routine post-partum uterine lavage. Miniature horses are at increased risk as they have a higher incidence of dystocia (difficulty foaling). The most common area to tear is the tip of the pregnant horns or the dorsal (upper) wall and these can be difficult to detect as the lacerations may not be palpable by your veterinarian.

Why should a uterine tear or rupture be classed as an emergency?

Large uterine ruptures often result in herniation and the mare will rapidly go into hemorrhagic shock, that may lead to death. These mares usually show signs of concern soon after parturition such as anxiety, sweating, increased heart rate and pale mucous membranes. Immediate veterinary assistance should be sought. Smaller tears can be more difficult to diagnose. Usually the mare develops generalized signs of peritonitis such as depression, lack of appetite, fever, reduced faecal output, reduced milk production, tacky mucous membranes, increased heart rate, mild colic signs and possibly vaginal hemorrhage or discharge. It is important as an owner to monitor the behavior of the mare closely, especially after a difficult birth, and seek veterinary advice if any of the clinical signs are noticed. Because these clinical signs are so generalized, other problems such as rupture of the uterine vessels, broad ligament haematoma, invagination of a uterine horn, colon torsion, endotoxemia or septic metritis may be the source. Seeking veterinary advice promptly should rule out or diagnose which problem is the underlying cause and can therefore be treated.

How will my veterinarian diagnose and treat a uterine tear or rupture?

If the mare has had a history of a difficult parturition and is showing clinical signs that are of concern, it is important to note that a vessel rupture (such as uterine vessel or broad ligament haematoma) generates very similar clinical signs. Therefore, minimizing stress to the mare to prevent disruption of a forming blood clot (which will stop the hemorrhage) is of the utmost importance. Your veterinarian will suspect uterine rupture or tearing from the history, eg a difficult parturition, by manual palpation, abdominal and transrectal ultrasound and abdominocentesis (commonly known as a belly tap; where a sample of peritoneal fluid is taken and analysed). Depending on the severity of the tear an exploratory laparotomy (abdominal surgical intervention) may be required, where the rupture is surgically repaired. Smaller tears can sometimes be managed conservatively. The mare will need to be hospitalized and the neonatal foal may either require supplemental feeding or fostering depending on the mare’s condition and recovery, as the mare may have a lack of milk/not be well enough to feed the foal.

What is the prognosis for survival after a uterine tear or rupture?

Prognosis depends on the thickness and size of the tear and the degree of contamination in the abdominal cavity. If the uterine tear or rupture is detected quickly and treated promptly (within 24 hours of rupture) the prognosis for survival is relatively good (approximately 80%). Mares that develop severe peritonitis or establish endotoxemia however, have a more guarded prognosis as many of these cases experience peri- or post-operative complications such as ileus, thrombophlebitis and laminitis.

Can I still breed from a mare after she has had a uterine tear or rupture?

Depending on the extent of the tear and the healing process, mares having recovered from a uterine tear or rupture may be more prone to complications in future pregnancies. This is due to the scar tissue produced in the ruptured area making the uterine lining less elastic and versatile after healing. It is therefore advised that owners discuss further potential breeding with their veterinarian prior to conception.